I just pumped using AMEX on Wednesday, 9 Sept'15. Swiped at the kiosk machine.

Probably try using a different pump? There's one pump at the station near my house which rejected my AMEX a few times already (but other kiosk pumps' machine accept). Hence I always avoid using that particular pump (not sure if it has been fixed, but too much hassle of having to move to a different pump later if it still doesn't work)